The invention relates to compositions which may be used in the automotive industry, particularly as additives in the preparation of automotive sealants.
In the manufacture of automobiles, the bodies and frame assemblies thereof are coated, or primed, electrostatically with a 100 percent solids powder spray. The compositions of such powder sprays, referred to in the automotive industry as xe2x80x9cpowder primexe2x80x9d, and methods of electrostatically applying the powder prime are well known to those skilled in the automotive industry. It is estimated that on the order of 25,000 pounds per month of 100 percent solids waste powder prime may be generated at each assembly plant in which it is used to prime auto parts, such as frame assemblies. The waste powder prime, that prime which does not remain affixed to the primed auto part and which is recovered subsequent to the electrostatic deposition of the powder prime thereon, currently is being transported to landfills for disposal. It would be considered to be a significant environmental advance and contribution if one were to discover a use of waste powder prime, such that the present practice of disposing of waste powder prime in landfills could be reduced significantly, or totally eliminated.
Also in the manufacture of automobiles, automotive sealants are used in order to prevent air, water and dust intrusion into the passenger compartment of the automobile. These sealants typically are made of plastisols, those being mixtures of plasticizers and polymeric resins such as poly(vinyl chloride), poly(vinyl acetate), or copolymers of vinyl chloride and vinyl acetate. Other polymers may be used as well in preparation of the plastisols. The sealants further may contain ingredients such as fillers, for instance calcium carbonate, talc, calcium oxide, and glass hollowspheres; rheological additives such as thixotropes, for instance silicas and clay derivatives, and pigments, for instance titanium dioxide and carbon black. Because the adhesion of a plastisol to cold-rolled-steel or electrodeposition coatings (E-coat) is poor, conventional sealants must contain adhesion promoters. The most common of the adhesion promoters used in preparation of the sealants is polyamidoamines. Without the adhesion promoters, such sealants will exhibit poor adhesion to such substrates as cold rolled steel and the E-coat.
It has been reported that waste paint sludge which is recovered from automotive xe2x80x9cpaintingxe2x80x9d processes and which contains water, solvent and uncured polymer, may be used in the preparation of automotive sealants. However, before the waste paint sludge may be used to prepare automotive sealants, the waste paint sludge must undergo extensive treatment and processing to remove all or most of the water or solvent from the waste sludge. The xe2x80x9cpaintingxe2x80x9d operations from which the waste sludge is recovered differ from the xe2x80x9celectrostatic depositionxe2x80x9d from which the waste powder prime is recovered. The powder prime never contains water or solvent, either as a virgin material or as a waste material. Additionally, the powder prime does not utilize ingredients such as tackifiers, plasticizers and coalescents, which commonly are used in film-forming xe2x80x9cpaintsxe2x80x9d formulated with water and/or solvents.
The present inventors surprisingly have discovered that waste powder prime may be used, without further recycling or treatment, in order to formulate compositions which may be used in the automotive industry. Specifically, the inventors surprisingly have discovered that waste powder prime may be used in combination with specific plasticizers in order to prepare compositions which may be used as additives in the automotive industry. In particular, the additives are used in the preparation of automotive sealants.
The inventors can identify at least three distinct advantages of their invention over the prior art paint sludge. First, the waste powder prime requires no processing to remove unwanted solvent or water prior to its use in the preparation of automotive sealants. Second, the waste powder prime typically is free or essentially free of components such as tackifiers, plasticizers and coalescents, which commonly are used in film-forming xe2x80x9cpaintsxe2x80x9d formulated with water and/or solvents. As a result, in the formulation of compositions which utilize waste powder prime, the formulator need not be concerned with detrimental affects such components might have on the particular formulated compositions. Finally, the present invention provides a practical and economical solution to a significant environmental need by reducing or eliminating the amount of waste powder prime which is disposed of in landfills, without the need for extensive and expensive recycling processes, while unexpectedly providing improvements in automotive compositions which have not been reported heretofore. It is believed that each of the above advantages in and of itself constitutes a significant improvement over the prior art xe2x80x9cpaint sludgexe2x80x9d containing water and solvent, as discussed above. In addition to the fact that all three of the above advantages may be realized simultaneously, the compositions of the present invention offer other advantages which are disclosed herein below.
The present invention is directed to compositions which may be used as additives in the automotive industry, which compositions comprise waste powder prime (WPP) and a plasticizer selected from the group consisting of 2-ethylhexyl diphenyl phosphate, diisoheptyl phthalate, a linear phthalate based upon C7-C9 alcohols, a mixture of esters, and dipropylene glycol dibenzoate. When used as an additive, in the preparation of formulated automotive sealants which are substantially free of an adhesion promoter, or preferably which are free of an adhesion promoter, the inventive additives provide sealants which exhibit adhesion which is as good as or better than conventional automotive sealants which do contain an adhesion promoter in conventional amounts used to provide adhesion to automotive sealants. Also included within the scope of the present invention are automotive sealant compositions which comprise a polymeric resin, WPP and a plasticizer selected from the group consisting of 2-ethylhexyl diphenyl phosphate, diisoheptyl phthalate, a linear phthalate based upon C7-C9 alcohols, a mixture of esters, and dipropylene glycol dibenzoate.